An Efficient Trajectory Generation for Bi-copter Flight in Tight Space

TL;DR

This paper tackles the challenge of planning efficient and safe trajectories for elongated bi-copters navigating narrow environments, where traditional mass-point planning is inadequate. It combines a whole-body collision-free path search in SE(2) with differential flatness to produce a feasible initial path, then jointly optimizes position and yaw using a MINCO-based spatial-temporal trajectory, constrained by dynamic feasibility and collision avoidance via penalty terms. A novel safe flight corridor generation around oriented bounding boxes guarantees full-body collision-free envelopes, improving robustness in tight passages. Extensive simulations and real-world experiments across scales validate improved smoothness (lower jerk) and shorter planning times, enabling reliable bi-copter passage through gaps as small as a fraction of the vehicle width, with onboard computation and perception. The approach advances practical narrow-space navigation for rectangular multirotor platforms and offers a transferable framework for further height-variant extensions in $\mathbb{R}^3 \times SO(2)$.

Abstract

Unlike squared (or alike) quadrotors, elongated bi-copters leverage natural superiority in crossing tight spaces. To date, extensive works have focused on the design, modeling, and control of bi-copters. Besides, a proper motion planner utilizing bi-copters' shape characteristics is essential to efficiently and safely traverse tight spaces, yet it has rarely been studied. Current motion planning methods will significantly compromise their ability to traverse narrow spaces if the map is inflated based on the long dimension of the bi-copter. In this paper, we propose an efficient motion planning method that enables the safe navigation of bi-copters through narrow spaces. We first adapt a dynamic, feasible path-finding algorithm with whole-body collision checks to generate a collision-free path. Subsequently, we jointly optimize the position and rotation of the bi-copter to produce a trajectory that is safe, dynamically feasible, and smooth. Extensive simulations and real-world experiments have been conducted to verify the reliability and robustness of the proposed method.

Figures (7)

• Figure 2: Flight corridor generation in narrow environments. (a): The intersection of two adjacent polyhedrons is too slim, failing to accommodate the bi-copter's body width. (b): The intersection of two adjacent polyhedrons is insufficiently small.
• Figure 3: Test platform of proposed bi-copter. (a): System of the bi-copter platform. (b) Bi-copter platform with extended size.
• Figure 4: Whole-body collision check of bi-copter, the blue rectangle is the orientated bounding box of the whole-body of bi-copter, black grids are the obstacle, and gray ones are grids that need to be checked for collision.
• Figure 5: Evaluating the proposed method against WBFP. (a): Proposed method. (b): WBFP
• Figure 6: Comparative analysis of varying sizes bi-copters. (a): $0.2m \times 1.2m$. (b): $0.3m \times 1.2m$. (c): $0.4m \times 1.0m$